As a cutting insert (hereinafter also referred to simply as “insert”) for use in a cutting process of workpieces, such as metals, a cutting insert described in Japanese Unexamined Patent Publication No. 2010-523352 (Patent Document 1) is known. The insert described in Patent Document 1 includes a major flank surface extending from a major cutting edge close to an upper surface toward a minor cutting edge close to a lower surface, and a minor flank surface extending from the minor cutting edge close to the upper surface toward the major cutting edge close to the lower surface. The major flank surface is inclined so as to depart from a central axis of a through hole as going from the upper surface toward the lower surface. The minor flank surface is inclined so as to approach the central axis of the through hole as going from the upper surface toward the lower surface. The insert described in Patent Document 1 is configured to be attached to a tool body (holder) by a bolt (screw) to be inserted into the through hole. On this occasion, the two major flank surfaces on a side surface come into contact with the tool body.
When a cutting process is carried out using the insert described in Patent Document 1, a force is applied to the major cutting edge and the minor cutting edge used for cutting in a direction from the upper surface toward the lower surface. Therefore, as a reaction against the force, a force is apt to be applied to the two major flank surfaces being in contact with the tool body in the direction from the lower surface toward the upper surface.
Here, the major flank surface is inclined so as to depart from the central axis of the through hole as going from the upper surface toward the lower surface, thus making it easier for the insert to slide toward a workpiece. This makes it easier for the insert to slide laterally with respect to the through hole configured to accept insertion of the bolt. Accordingly, the bolt can be subjected to a large lateral load, namely, a large shear stress. It can therefore be difficult to stably fix the insert to the holder.
The present embodiment has been accomplished in view of the above problem, and provides a cutting insert capable of being stably fixed to the holder.